Just a quick post to point you all over to a fantastic resource on
How to Read and Understand the OSPF Database
Written by Alfred Lumbis who I believe is a Cisco employee it goes through step by step what you need to do to fully understand the OSPF database
Extract:
OSPF, being a link-state protocol, allows for every router in the network to know of every link and OSPF speaker in the entire network. From this picture each router independently runs the Shortest Path First (SPF) algorithm to determine the best path through the network. All of this information is stored in the "Link State Database" (LSDB). Every network engineer has seen the LSDB at some point by running show ip ospf database but few actually know how to read the details. By looking only at the LSDB we should have enough information to draw a topology diagram from scratch.
Read the full post here
